Gym operators have another reason to discourage members from skipping leg day: People with strong legs were less likely to develop heart failure after a heart attack.
High quadriceps strength level, compared to low quad strength level, lowered the risk of developing heart failure by 41 percent, according to a study presented May 20 at Heart Failure 2023, a scientific congress of the European Society of Cardiology (ESC).
“Our study indicates that quadriceps strength could help to identify patients at a higher risk of developing heart failure after myocardial infarction who could then receive more intense surveillance,” study author Kensuke Ueno, a physical therapist at the Kitasato University Graduate School of Medical Sciences, Sagamihara, Japan, said in a media release. “The findings need to be replicated in other studies, but they do suggest that strength training involving the quadriceps muscles should be recommended for patients who have experienced a heart attack to prevent heart failure.”
The study of 932 people between the ages of 57 and 74 hospitalized in 2007 to 2020 with acute myocardial infarction found that those with what was determined as “low” leg strength had a higher incidence rate of subsequent heart failure (at 22.9 per 1,000 person-years) than those with “high” quadriceps strength (at 10.2 per 1,000 person-years). (Person-years is defined as the number of people in a study multiplied by the number of years they were followed.)
A total of 451 patients had low quadriceps strength while 481 had high strength. During an average follow-up of 4.5 years, 67 patients (7.2 percent) developed heart failure.
Myocardial infarction (blockage of artery to the heart muscle) is the most common cause of heart failure, with around 6 to 9 percent of heart attack patients going on to develop the condition. Previous research has shown that having strong quadriceps is associated with a lower risk of death in patients with coronary artery disease. This study tested the hypothesis that leg strength is associated with a lower risk of developing heart failure after acute myocardial infarction.
Maximal quadriceps strength was measured as an indicator of leg strength. Patients sat on a chair and contracted the quadriceps muscles as hard as possible for five seconds, one leg at a time. A handheld dynamometer attached to the ankle recorded the maximum value in kilograms for each leg. The researchers used the average of both values.
Strength was expressed relative to body weight, meaning that quadriceps strength in kilograms was divided by body weight in kilograms and multiplied by 100 for a percent body weight value. Patients were classified as ‘high’ or ‘low’ strength according to whether their value was above or below the median for their segment.
The median value for women was 33 percent body weight. The median value for men was 52 percent body weight.
The researchers analyzed the association between quadriceps strength (low vs. high) and the risk of developing heart failure. The analysis was adjusted for factors known to be associated with the development of heart failure after myocardial infarction including age, sex, body mass index, prior myocardial infarction or angina pectoris, diabetes, atrial fibrillation, chronic obstructive pulmonary disease, peripheral arterial disease and kidney function.
The investigators also analyzed the association between quadriceps strength as a continuous variable and the risk of developing heart failure. Each 5 percent body weight increment in quadriceps strength was associated with an 11 percent lower likelihood of heart failure.